MAGNETOTELLURIC APPROXIMATIONS FOR THE ASTHENOSPHERIC DEPTH BENEATH THE BEKES GRABEN, HUNGARY

The paper describes the apparent changes of the depth of the conducting asthenosphere caused by different EM field distortions beneath the 7 km deep narrow 3-D Bekes graben (extensional basin) along the Pannonian Geotraverse. The real depth of the asthenosphere is approximated first by 1-D inversion and 2-D modelling techniques to show their value in case of 3-D structure. Then, 3-D thin sheet model computations-together with references to the previous theoretical modelling results-are used to select sites and curve orientation where the least distorted depth estimation is expected along a 2-D profile in case of 3-D structure. Of course, preliminary geological-tectonical information (e.g. basin contour) is needed to find the most probable asthenospheric depth.